A ζ-carotene desaturase gene, IbZDS, increases β-carotene and lutein contents and enhances salt tolerance in transgenic sweetpotato

zeta-Carotene desaturase (ZDS) is one of the key enzymes in carotenoid biosynthesis pathway. However, the ZDS gene has not been applied to carotenoid improvement of plants. Its roles in tolerance to abiotic stresses have not been reported. In this study, the IbZDS gene was isolated from storage roots of sweetpotato (Ipomoea batatas (L.) Lam.) cv. Nongdafu 14. Its overexpression significantly increased beta-carotene and lutein contents and enhanced salt tolerance in transgenic sweetpotato (cv. Kokei No. 14) plants. Significant up -regulation of lycopene beta-cyclase (beta-LCY) and beta-carotene hydroxylase (beta-CHY) genes and significant down-regulation of lycopene s-cyclase LCY) and epsilon-carotene hydroxylase (epsilon-CHY) genes were found in the transgenic plants. Abscisic acid (ABA) and proline contents and superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities were significantly increased, whereas malonaldehyde (MDA) content was significantly decreased in the transgenic plants under salt stress. The salt stress-responsive genes encoding pyrroline-5-carboxylate reductase (P5CR), SOD, CAT, ascorbate peroxidase (APX) and POD were found to be significantly up-regulated in the transgenic plants under salt stress. This study indicates that the IbZDS gene has the potential to be applied for improving beta-carotene and lutein contents and salt tolerance in sweetpotato and other plants.